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Armed with a mid-90 mph fastball that most deem to be a "plus" offering -- scouting jargon for beyond big league average -- the White Sox's No. 5 prospect shrugged and said he believed it to be only average. OK, he relented, maybe slightly above average.

Despite receiving an invitation to Chicago's Major League camp this spring, it's clear the 23-year-old right-hander is wary of becoming a one-pitch pitcher destined for the bullpen. He's intent on improving his secondary pitches -- a changeup and a slider -- necessary ingredients for a future in the rotation.

"I am working on throwing both at any given time so that hitters can't get too comfortable on two pitches; I'm trying to keep all three of them in their mind," the 2010 second-round pick said of his repertoire. "Once I master all three, I might look into developing a curveball or maybe a split or something, but that will be years down the road, once I get the grasp of these pitches."

Petricka finished 2011 in Class A Advanced Winston-Salem's starting rotation. He went 7-8 with a 3.65 ERA over a career-high 113 1/3 innings across three lower levels before working exclusively as a reliever in the Arizona Fall League. Impressing others, if not himself, in either role this month likely would lead to a spot with Double-A Birmingham.

MiLB.com asked Petricka to describe and grade each of the three pitches he employs, fastball included. (His grade is based on a scout's traditional 20-80 scale, 50 being Major League average.) Here is Petricka, in his own words:

Pitch one: Two-seam fastball

Origin: It's the only fastball I've ever thrown. It felt right going with the two seams as opposed to across the horseshoe -- I just grabbed the ball that way -- and I just always stuck with it. When I was in Little League, they accused me of throwing a breaking ball because it would always break the other way, but obviously, it wasn't; it was just a two-seam.

Purpose: I try to work it to both sides of the plate and use the movement to my advantage. The main thing for me is building off my fastball; the fastball is my best pitch and, until I establish that in any game, my other stuff just won't be any sharp.

Grip: I go with the two seams; I don't go across.

Speed: Anywhere from 90-94, 95. In shorter stints, it can get a little higher.

Grade: It's in the 50-55 range because it's already hard and it has the two-seam movement. My location with it could be better; that's what brings it down some.

Pitch two: Changeup

Origin: I learned it at [Iowa Western Community] College, when I was rehabbing from Tommy John in [2007-08]. We were talking amongst a couple teammates and we all agreed on what seemed like a good grip to go with it to make it look the most like a fastball.

Purpose: It's not a swing-and-miss pitch. It's a pitch you want them to hit but not hit well because they think it's the fastball and get the end of the bat on it and nub it out into the infield.

Grip: Circle-change. I grip it deep rather than letting it sit in my fingers and then throw it with the same arm action [as my fastball] and turn it over a tiny bit at the top.

Speed: I like it in the low 80s, especially if the fastball is in the low 90s because I want that speed difference. Sometimes I do get a little bit too much behind it, which, as long as I keep the same arm speed, can work. I just have to be careful with the location.

Grade: Maybe a 40, and that might be generous. I critique myself pretty hard.

Pitch three: Slider

Origin: It's been on and off the last couple of years. I had a bunch of coaches, and we were always trying to rotate the grip to find something that was comfortable, and I found many grips that would work for a little while, but then I would try and make it do too much. This past season in the Fall League, I found a slider that I'm very comfortable with. I'm just going to keep throwing it. I know it can be good at times, but I'm not consistent enough with it right now.

Purpose: I'd like to have the ability to purposefully throw it just below the zone, but I'd also like to throw it in any count; just 'cause until you can throw it for a strike, you shouldn't be trying to throw it for a ball.

Grip: I go to the long side of the horseshoe and then I bring my thumb up a little bit on the side vs. the bottom. I need to trust the grip and trust the pitch that I'm making and not force it.

Speed: It just comes out how it comes out. It's been a wide range. I can't even put a number on it because it's a new pitch.

Grade: Probably a 40. It shows promise, but the consistency is not there to be a big league pitch yet. And, hopefully, soon I can turn it into a big league pitch.

Andrew Pentis is a contributor to MiLB.com. Follow him on Twitter at @AndrewMiLB. This story was not subject to the approval of the National Association of Professional Baseball Leagues or its clubs.